Method implicitLoopWhen

tools/common/_hyperscript.iife.js:2571–2591

* Iterate over targets with a when condition, applying forward or reverse per element. * Supports async conditions transparently -- returns a Promise if any condition is async.

(targets, whenExpr, context, forwardFn, reverseFn)

     * Supports async conditions transparently -- returns a Promise if any condition is async.
     */
    implicitLoopWhen(targets, whenExpr, context, forwardFn, reverseFn) {
      var elements = [];
      this.implicitLoop(targets, function(elt) {
        elements.push(elt);
      });
      var conditions = elements.map(function(elt) {
        context.beingTested = elt;
        return whenExpr.evaluate(context);
      });
      context.beingTested = null;
      var hasPromise = conditions.some(function(c) {
        return c && typeof c.then === "function";
      });
      if (hasPromise) {
        return Promise.all(conditions).then((results) => {
          context.result = this.#applyWhenResults(elements, results, forwardFn, reverseFn);
        });
      } else {
        context.result = this.#applyWhenResults(elements, conditions, forwardFn, reverseFn);
      }
    }
    #applyWhenResults(elements, results, forwardFn, reverseFn) {
      var matched = [];
      for (var i = 0; i < elements.length; i++) {